what they mean is the partition tool you chose does or did not at the time support a GPT type disk.The util fdisk doesn't support GPT. Use GNU Parted
parted they claim is one partition tool that supports GPT.
2) I am not sure lilo is a GPT aware bootloader. grub2 has GPT support. There may be others.
Forgive my general ignorance, but what is the name of the Portues flavour you are attempting to install please?
3) In case you are interested, I have an internal 1TB drive with 4 primary partitions using the plain old MBR and not a GPT.
If you want lilo as a bootloader, and you don't mind losing any data, you can create a fresh parttion table MBR type with gparted and stay with Lilo if you wish.